By improving a topological structure of a network, a heterogeneous network realizes system performance optimization and becomes one of a research focus in mobile communications. The heterogeneous network is composed of a high-power macro base station planned by the network and a low-power node covered by the macro base station and placed independently, the low-power node, which includes a home base station, a micro-cellular and a relay station etc., can realize hotspot region coverage and cell service shunt, so as to obtain cell splitting gain. Since power and coverage of different base stations are different and the low-power node is placed independently, a interference problem of a control channel and a service channel of different base stations is very serious, and the heterogeneous network faces a huge technical challenge.
In a next generation evolving system, such as the 3rd Generation Partnership Project Long Term Evolution Advanced (3GPP-LTE-A standard), the interference problem is solved through an inter-cell interference coordination technology, which is an enhanced inter-cell interference coordination schemes (eICIC). The eICIC is one of symbolic key technologies in the LTE-A and used for improving cell edge coverage and realizing the cell service shunt, such as coverage range extension (RE). The eICIC is mainly divided two types: the first one is an eICIC scheme based on a carrier aggregation technology, and the second one is a scheme based on a time-domain almost blank subframes (ABS). A service silence is realized by the ABS through allocating ABS subframes in an interference cell, and user interfered strongly in an original cell is served by the interfered cell through using the ABS subframes, so as to realize inter-cell interference coordination.
A carrier aggregation technology, which is one of key technologies of the LTE-A, is capable of providing high-speed service in a large bandwidth formed through aggregation, and further realizing frequency domain interference avoidance of the heterogeneous network at a component carrier (CC) resolution level. Supposing that a bandwidth of the heterogeneous network is composed of two component carriers: f1 and f2, in order to realize the interference coordination between the macro base station and the femto base station, the f1 and f2 are respectively allocated to users of the macro base station and the femto base station, so as to realize the interference avoidance of the service channel and the control channel of users; or a cell center user of the femto base station is configured with a CC same to the macro cell, and an edge user is configured with a CC different from the macro base station. However, a defect of this scheme is that it can be used by an LTE-A user only, and not compatible to an LTE user. An application of above-mentioned technology is in an important condition of firstly solving a service cell selection problem of users in a cell. In a cellular mobile communication network, all users have a home service cell, which is used for providing service of broadcasting, service transmission etc. for users. In a traditional homogeneous network, a service cell selection of a user is based on a measurement of received signal intensity. In the heterogeneous network, since a transmitting power of newly added node is lower than the macro base station, a coverage range of the newly added node is small through a method for selecting a service cell based on received signal intensity, and cell splitting gain maximization is not realized. In order to improve a priority of a low-power node, extend a coverage range of the low-power node, an enhanced LTE-A heterogeneous network cell selection and re-selection algorithm is proposed in research and discussion of a 3GPP session, mainly refers to a RE algorithm and a path loss algorithm proposed by a Qualcomm Incorporated. An core concept of the RE algorithm is: in traditional service cell selection algorithm, a bias value larger than 0 is added to the reference signal receiving power (RSRP) of the low-power node, and a RSRP compensation value bias for the macro cell is 0, so as to lower a threshold of the low-power node, and increase a probability of an User Equipment (UE) for selecting the low-power node as the service cell. In the cell selection algorithm based on the path loss, a cell with minimum path loss is selected as the service cell by the UE.
The coverage range of the low-power node is extended observably through the above method, which is almost similar to the macro cell. As for users on the coverage edge of the low-power node, even an effect of strong interference source is eliminated through interference elimination measures, a downlink signal to interference plus noise ratio (also called signal to interference plus noise ratio, SINR) is very low, which is caused by the low transmitting power of the service cell (low-power node), thus, a cell spectral efficiency is low.
When multi-antenna technology is used, the inter-cell interference coordination can further be performed in a spatial domain, such as a coordination multi-point (CoMP) transmission technology, through a interaction of mobile user channel information of adjacent cells, a certain interference avoidance policy is applied to the edge user by adjacent cell or combined transmission is applied to the mobile user by multiple cells, so as to improve a throughput capacity of the edge user and a coverage of high-speed data transmission, reduce the interference of the edge user, and increase a cell throughput capacity. In the heterogeneous network, the CoMP acts as an enhanced technology of an eICIC technology, and further increases system capacity based on gain obtained by the eICIC.
At present, an inter-cell coordination beam avoidance algorithm is mainly adaptive to the homogeneous network. In a heterogeneous network scene, there is a large difference in a SINR distribution of cell users, then an effectiveness of traditional interference avoidance algorithm, such as a zero forcing algorithm, a signal to leakage and noise ratio (SLNR), algorithm, is greatly reduced, meantime, the beam avoidance algorithm will be limited by a quantity of antenna along with increasing of density of the low-power node, and freedom is limited.
As mentioned above, the related technical solution has following technical problems:
(1) a large number of edge users occur along with an introduction of the low-power node, a currently-used method for selecting a beam is based on an assumption of the homogeneous cell, but in the heterogeneous network, a beam selection of users is greatly affected by a SINR distribution of different types of cells;
(2) the low-power node introduced in the heterogeneous network uses a multi-antenna technology, as for dense heterogeneous network, a performance of existing method is limited by the freedom.